Electric discharge device.



W.-R. WHITNEY.

ELECTRIC DISCHARGE DEVICE.

APPLICATION man NOV. 6. 1914.

E Patented May 28,1918.

ig in Witnesses: 2.9 M 2% %.Q/% /7 lit) - tpeetttton or new tatent.

YUNA, NEW YORK, ASSIGNOR T0 GEI'IJEF-MD ELECTRIG t: ORATIOBI 0F Jtl' TOEa; an nnvronl Fatend ay II pp'lttton tied November t, 191a. serial no.traces.

To all whom it may concern."

Be it known that I, time R. v, a citizen of the United States, residmgat Niska na, county of Schenectady, State of New ork, have inventedcertain new and useful Improvements in Electric Discharge Devices, ofwhich the following is a specification.

The present invention relates in general to electric'discharge deviceshaving a cathode operating at incandescence, and the ob-. ject of myinvention is to suppress local (llS- integration or erosion of thecathode near its supports and thus to lengthen the life of theapparatus.

In inclosed are devices in which a cathode of refractory materialoperates at incandescence, the regions of the cathode near the supports,or in some cases a region of the support adjacent the cathode proper, iseaten away or disintegrated by some electrical action quite apart fromthe thermal evaporation, and which appears to be due to a bombardment bypositive ions.

In accordance with my invention I provide a protecting means operatingto prevent this local electrical disintegration of the cathode. Thismeans proba ly operates by discharging the positive ions and may consistof a conductor extending into their path and maintained negativelycharged. In one embodiment of my invention this discharging conductor isconstituted by a'conductive shielding means electrically connected tothe cathode support and surrounding the region to be protected. Thisshield apparently operates to prevent the access of positive ions to thecathode. The electrical erosive action is transferred to the shieldwhere it can do no harm. In examples of my invention hereinafter morefully de scribed the shield means assumes the form of a sleeve spacedaway from the cathode and interposed between the region of the cathodesubject to disintegration and the anode.

My invention is applicable to various types of discharge devicescontaining an incandescent metal acting as a cathode, and theaccompanying drawings illustrate two examples of devices embodying myinvention. Fi re 1 shows a rectifier; Fig. 2 shows an inc osed arc lamp;Figs. 3 to 5, inclusive, illustrate" on an enlarged scale specific formsof my invention.

The particular term! of rectifier shown in F1g. 1 as illustrating oneapplication of my nvention, comprises an envelop 1 consistmg of glassand provided with side arms 2, 2, for the convenience of the sealing-inot the anode terminals. The envelop is filled wlth an inert gas, such,for example, as nitrogen, argon, neon or mercury vapor or mixtures ofthese gases at a pressure rangmg usually from about a centimeter ofmercury to atmospheric pressure." When the arc is to operate in mercuryvapor a globule of mercury 3 is provided and the envelop proportioned torun at a temperature at which the mercury vaporized will have thedesired pressure. In the case of mercury vapor this pressure in somecases may be as low as about one millimeter.

The cathode 4:, as more clearly shown in 3, consists of a conductor ofsome highly re ractory material, such as tungsten, which in this case ishelical although it may assume other forms. This cathode is connected tocurrent conveying supports 5, 6, also preferably consisting of tungstenand sealed directly into the stem 7 of low expansion glass. In case theenvelop itself does not consist of low expansion glass 'but consists ofa glass having a difi'erent coeficient of expansion, for example leadglass or consists of quartz, a stem of low expansion glass may be joinedthereto by a graded seal. The anodes 8, 9 may have any convenient form,in the present instance con-.

sisting of spirals of tungsten or other refractory metal. They areconnected respectively to the supports 10, 11 sealed into stems 12, 13.It is not necessary that two sup ports should be provided for eachanode, but it is obviously convenient to support a spiral in thismanner.

At the respective ends of the cathode 4e are provided shields 14, 15,also preferably consisting of tun ten, although other metals such amolyb enum or iron may also be used. These shields in the deviceillustrated are attached to and electrically connected with thesupporting wires 5, 6, and extend over the end turns of the cathode, asshown in Fig. 3. It is not necessary that the shields should have theparticular form shown in Fig. 3 in which they are constituted of closelyWound wire, but as shown in Fig. 4, in connection with'the electrodesout an arc lamp, the shields 16, It, consist ot ltllt llt spirals, theturns of which are spaced apart, and in Fig. the shields 18, 19 consistof imperforate tubes.

The bombardment of the cathode by the positive ions with an acco anyingabrasion appears to be greatest near he ends of the cathode. This may beconnected with the fact that at this region the cathode is cooled by theconduction of heat away from the cathode-through the lead but moreprobably is largely due to the fact that the positive ions bombard themost negative parts of the cathode, namely the terminals. As the shieldsextend into the path of the positive ions and being electricallyconnected to the supports, are maintained at the potential of thesupports, the bombardment is received by the shields. Somedisintegration of the shields occurs but as they may be made relativelyheavy and are unheated, the erosion does little or no harm. As alreadyindicated my invention is applicable to various types of dischargedevices, and in Fig; 2 has been shown applied to a miniature are lamp.

The electrodes 21, 22 of refractory metal operate at incandescence in anatmosphere of inert gas, for example, nitrogen, argon, or mercury vaporfurnished by a globule of mercury 23, when an arc is struck between theelectrodes in any convenient manner, for example, by a high potentialdischarge. The envelop preferably is proportioned and the initial gaspressureso chosen that the pressure when the lamp is operating is ofabout the order of atmospheric pressure. The electrodes 21, 22 arecarried by supports 24, 25 of tungsten or other refractory metal sealedinto a stem 20. In order to reduce the heat losses from the electrodes21, 22 to enable them to operate at highest incandescence, theypreferably are connected to the main supports 24, 25 by stems 26, 27 ofreduced diameter, and it is particularly these stems that are subject todisintegration. Each is heated to a temperature intermediate the wor ngelectrode and the support chiefly by conduction from the heatedelectrodes. The shields 16, 17, as already explained, may consist ofspirals, Fig. 4, or of tubes 18, 19, Fig. 5. These shields extend thepotential of the supporting and they protect the same from thedisintegrating efi'ect of positive ions. In the lamp illustrated theelectrodes 21, 22 have substantially the same size and are intendedparticularly for operation with alternatin current and hence eachoperates alternately as cathode. Each electrode, therefore, has beenprovided with protecting shields. In a lamp designed for direct currentoperation it is not necessary to provide a shield for the anode.

It should be understood that the particuwires around the stems velop, anincandescing electrode mounted therein, a current-conveying conductortherefor and a conductive shield mounted upon 'said conductor andextending around the negative end of said electrode but spaced aparttherefrom.

2. In an electrical arc device comprising a container, a gaseousatmosphere at a pressure of at least about one millimeter of mercury, acathode operating at incandescence, a support for said cathode and aconductive shield spaced away from said cathode and electricallyconnected directly to the support, and extending about an end of thecathode only to the exclusion of the remainder of the cathode.

3. An electrical device operating by gas ionization comprising anenvelop, a gaseous filling therein, a cathode operating at incandescenceone region of which operates relatively cooler than the remainingportion, a cooperating anode, and a shield electrically connected tosaid cathode and interposed be tween said cool region of the cathode andsaid anode.

4;. In a vapor electric device comprising a container, a gaseous fillingtherein, at a pressure high enough to permit of ionization, an electrodeoperating at incandescence, a support therefor, a shield surrounding thejunction only of said support and said electrode, and receiving thedisintegrating effect of positive ionization, thereby protecting thecathode.

5. A vapor electric device comprising an envelop, a cathode operating atincandescence, supports therefor connected to said cathode, an anode, agaseous atmosphere surrounding said electrode and a shield locatedbetween the region of the cathode adjacent the support and the anode.

6. A device comprising a container, a gas therein, at a pressure highenough to permit of ionization, a cathode of refractory materialoperable at incandescence, terminal conductors therefor and conductiveshields surrounding the parts of the cathode adjacent the terminalconductors, said shields g being maintained at the potential of theterminal conductors.

7. A device comprising a container,

a gas therein, at a pressure high enough to permit ionization, a cathodeof refractory material operating at incandescence, one region of whichis subject to local destructive electrical disintegration, and adischarge-receiving shield located adjacent said region of the meme?llilfit;

cathode but leaving other paints of the cethi In witness whereof, I havehereunto set ode expoeedl. my handl this 5th day of November, 1914:.

8. The method of protecting en incendes- WILLIS R. HNEY. eent cathodeoperating in a. gee from electri- Witnesses: 5 mil erosion whichoensists in mninteining in IWARY E. m 1: an, the vicinity of saidcathode 8t conductor BENJAMIN B. H

negative with respect to seiei cathode.

